US Patent 7688622 Phase change memory device with dummy cell array

A phase change memory device includes a cell array having a phase change resistance cell arranged at an intersection of a word line and a bit line and a dummy cell configured to discharge the bit line in response to a first bit line discharge signal. A column switching unit selectively controls a connection between the bit line and a global bit line in response to a column selecting signal. The dummy cell disconnects a discharging path in response to the first bit line discharge signal in a precharge mode, and discharges the bit line in response to the first bit line discharge signal in an active mode.